The present invention relates to a metering device, particularly for capsule-filling machines. In conventional capsule-filling machines, the product to be packaged is picked up in doses from a rotating bowl by means of a metering unit and transferred into capsules. The capsules comprise a bottom and a cap made, for example, of hard gelatine. Before being filled with product, each capsule is opened, i.e. its cap is removed from the bottom and the latter is then ready to receive a dose of product coming from the metering device. The metering device usually comprises a punch member which is arranged to enter with its lower end a bowl of product and to fill a cavity formed in this end with product by the combined action of penetration of the punch member and of pressure against the product and thus against the bottom of the bowl.
Conventional metering devices, however, have the disadvantages that vacuum spots are created in the doses of products picked up by the punch member, the vacuum spots being caused by non-uniform arrangement and stratification of the product. This drawback is prejudicial to the obtainment of perfect metering as the metering punch member penetrates in a non-compact and homogeneus state, and thus it will pick up different amounts of product depending upon the stratification rate in the various zones of the product in the bowl. This undesired phenomenon is prejudicial to the possibility of conveniently processing and manipulating products which due to their nature have low flowability and difficult to give raise to stratification, as well as very bulky products which are liable to remain in suspension.
In conventional capsule-filling machines, the above mentioned kinds of products can be handled only by adding eccipient agents capable of giving the product particular and desired flowability and stratification characteristics that otherwise they would not possess. However, this operation often gives rise to a remarkable increase in volume of the dose of product to be loaded into single capsules and thus it is necessary to make use of capsules of larger sizes, to adopt supplementary mixing operations, possible granulation, which results in higher costs of production.